This invention relates generally to irrigation management, and more particularly concerns a system which conserves water and energy by providing optional or highly efficient irrigation to growing plants.
The most basic form of present irrigation control involves a decision by a human to begin or discontinue application of irrigation water. The effects of under-irrigation are obvious in that plant condition suffers; however, in many cases over irrigation does not cause apparent harm to the plants. In such a case, the major harm caused by over-irrigation is the waste of irrigation water and the energy required for its distribution. Additionally, however, there may be subtle but significant impairment of plant growth.
Several methods have in the past been developed to improve the efficiency of irrigation and at the same time minimize the burden on human operators. One technique is the use of preprogrammed timers to automatically start and terminate irrigation. Such timer systems can be enhanced to provide for multiple timing cycles which vary in accordance with plant growth cycles. However, such systems have the limitation that there is no feedback between actual plant water consumption and water application. For example, timer systems are unable to reduce water application during times of humid or rainy weather, and do not account for variable water requirements.
Because of these limitations, systems which measure free soil moisture were devised. Such systems measure soil moisture in a variety of ways, including soil electrical conductivity, and by use of tensiometers. Typically, water application is commenced when the soil moisture is diminished to a preset level; and discontinued irrigation when the moisture again rises to a predetermined level. Such operation has several limitations, relating primarily to the time delay between the application of irrigation water, and the measurement of changes in the soil moisture at depth. For example, the moisture sensors at depth may still be wet when shallower plant roots are already becoming dry. Similarly, the irrigation water may not have reached the sensors even when the surface has been flooded with water.
Efforts to overcome these problems have involved the combining of timers with soil moisture sensors. In such systems, the timers actuate irrigation at predetermined times, but only if the moisture soil sensors indicate that the soil has become dry. The timers eliminate the danger of overwatering while waiting for moisture to penetrate to the sensors. Still, they are not responsive to changes in weather, nor can they sense any characteristics other than the simple value of the soil moisture.
Another broad aspect which has been addressed previously is the concept of using telemetry to acquire data from the agricultural field, and to use data to obtained to actuate irrigation controllers. Systems described heretofore, however, lack sufficient control.